1970 Nova L78 Intake '569' - perfomance!!

[Bahnz70]

I am finishing my 1970 L78 Nova, this was a former racecar (stock) and when I bought the car the '291' heads were in the trunk and it had aftermarket aluminum heads on the car. I am leaving them on and building kind of a day 2 street car. My question is I currently have the '569' intake on the car but my engine man says that I could probably gain about 50hp with an aftermarket intake. How well does this stock intake flow (they put it on the LS6 cars) and does a '163' from 69 flow better or should I go aftermarket (edelbrock, Holley, Weiand) and what aftermarket is best.
Thanks for all of the input...